<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body style="margin: 50px;">
	<table border="1" width="1000">
        <tr style="background-color: #999;">
            <th><input type="checkbox"></th>
            <th>分类ID</th>
            <th>分类名称</th>
            <th>分类描述</th>
            <th>操作</th>
        </tr>
        <tr>
            <td align="center"><input type="checkbox" name="chekbox"></td>
            <td>1</td>
            <td>手机数码</td>
            <td>手机数码类商品</td>
            <td><a href="">修改</a>|<a href="">删除</a></td>
        </tr>
        <tr>
            <td align="center"><input type="checkbox" name="chekbox"></td>
            <td>2</td>
            <td>电脑办公</td>
            <td>电脑办公类商品</td>
            <td><a href="">修改</a>|<a href="">删除</a></td>
        </tr>
        <tr>
            <td align="center"><input type="checkbox" name="chekbox"></td>
            <td>3</td>
            <td>鞋靴箱包</td>
            <td>鞋靴箱包类商品</td>
            <td><a href="">修改</a>|<a href="">删除</a></td>
        </tr>
        <tr>
            <td align="center"><input type="checkbox" name="chekbox"></td>
            <td>4</td>
            <td>家居饰品</td>
            <td>家居饰品类商品</td>
            <td><a href="">修改</a>|<a href="">删除</a></td>
        </tr>
    </table>
    <script>
        let objTableRows = document.getElementsByTagName("tr");
        for(let i = 1;i < objTableRows.length;i ++){
            if(i % 2 === 0){
                objTableRows[i].style.backgroundColor = "blue";
            }
        }
    </script>


</body>
</html>